Re: [Qemu-devel] [PATCH] target-moxie: Add moxie Marin SoC support

[Andreas Färber]

Hi,

Am 15.12.2013 13:48, schrieb Anthony Green:
> Peter Crosthwaite <address@hidden> writes:
>> On Sun, Dec 15, 2013 at 1:59 PM, Anthony Green <address@hidden> wrote:
>>> diff --git a/hw/moxie/marin.c b/hw/moxie/marin.c
>>> new file mode 100644
>>> index 0000000..0a998e4
>>> --- /dev/null
>>> +++ b/hw/moxie/marin.c
>>> @@ -0,0 +1,167 @@
>>> +/*
>>> + * QEMU/marin SoC emulation
>>> + *
>>> + * Emulates the FPGA-hosted Marin SoC
[...]
>>> +static QEMUMachine marin_machine = {
>>> +    .name = "marin",
>>> +    .desc = "Marin SoC",
>>
>> So SoCs should generally be implemented on two levels. There is the
>> SoC device, which contains the devices that are on the SoC chip, then
>> the board level instantiates the SoC. This looks like a flat
>> board-and-SoC in one (on board level). Your deisgn is trivial so far
>> (and good for a first series), but long term what is the organsation?
>> Is this going towards a particular board emulation? Have a look at
>> Liguangs Allwinner series (and some of the early review comments) for
>> a discussion on this topic:
>>
>> http://lists.gnu.org/archive/html/qemu-devel/2013-11/msg03940.html
>>
>> As a starting point, can you tell us what is and isn't hosted on the
>> FPGA in this board model? That might be the best way to split this.
> 
> The Marin SoC currently runs on two boards: the Nexys3 (Xilinx) and DE-2
> (Altera).  They are pretty much identical from the software side of
> things.  Marin currently provides the UART, PIC, 7 segment display and
> timer devices, as well as various memory controllers.  There's no useful
> distinction between SoC and board at this time.  I'd like to keep it
> simple as per my patch rather than try to factor them out prematurely.

I thought I've seen a number of odd embedded systems already, but I'm
having trouble understanding your combination of SoC and FPGA: Xilinx
and Altera both have SoCs combining a Cortex-A9 with an FPGA. But your
reference to Xilinx and Altera boards rather sounds as if Moxie is used
as a soft-core processor on the FPGA? In that case the term "SoC" would
be really confusing to me... Can you clarify or aid with some links?

Regards,
Andreas

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